Poison ivy, poison oak and poison sumac each has a sap that is composed of substances that provoke a sensitizing reaction in most people the first time contact with the sap occurs. After a person has become sensitized, subsequent contact with the sap produces an allergic reaction. First, the skin reddens and begins to itch. Small watery blisters appear and the inching becomes worse. Persons with poison ivy commonly scratch which slows healing and may spread the active substances from the plant's sap to other locations on the body. Boric acid solutions or calamine lotion have been used to relieve itching with only limited success.
It is fairly common for a person, when partaking in an outdoor activity, to come into contact with poison ivy and plants that cause an allergic response. Similarly, some people have an allergic response to insect bites, foods and other agents that result in the formation of itchy watery blisters like those caused by an allergic response to poison ivy. Substances that cause allergic reactions such as those described above are referred to herein as "allergens". A remedy that reduces rash formation and itching of the skin caused by these types of allergic reactions is desirable.